This invention relates to an arrangement for a strain-relief mounting of the connecting points of strand connectors, that are reinforced by means of clamp plates or by soldering, in pocket-type hollow spaces of a coil-insulating part of the stator of a small, preferably external rotor type, electric motor. The pocket-type hollow spaces extend axially of the rotor axis and are formed on an external shell surface of a cylindrical collar of an end plate, arranged on the front surface of a stator plate bundle.
In (DE-PS No. 21 36 170), an arrangement for the strain relief mounting of strand connectors of small electric motors is provided for an external rotor motor. Pocket-type hollow spaces are arranged in the coil-insulating part, which is arranged on the front side of the stator that is opposite the fastening side, and is enclosed by an external rotor bell. The spaces extend in radial direction and are equipped with an insulating covering, such as a small plate of insulating material or a tongue. The strand connectors, at their reinforced connecting points, are fitted into the pocket-type hollow spaces and are guided, after a one-time rectangular deflection, through an axial groove of the stator to the fastening side of the external rotor motor.
In this axial groove of the stator, the strand connectors are subjected to increased coil temperature. Thus, strand connectors of this type must be equipped with a high-quality insulating-material jacket and are therefore more expensive than ordinary strand connectors that do not have to withstand high temperature stress.
In addition, the threading, or inserting, of the strand connectors into the axial groove of the stator requires additional working time, making manufacturing more expensive.
This invention has an objective of providing an arrangement of the initially mentioned type, particularly for external rotor motors, that permits the use of less heat resistant strand connectors; also the arrangement makes possible the mounting of reinforced connecting points of the connector strands to coil wire ends of the stator in pocket-type hollow spaces of a coil-insulating part of the stator, which arrangement is simpler with respect to manufacturing technology and nevertheless relieves strain.
According to the invention, this objective is achieved by having pocket-type hollow spaces arranged in pairs next to one another, and separated from one another in an insulating way. The pocket-type hollow spaces are arranged at an end plate on the side of the fastening and, on the insertion side, are covered by a ring-shaped insulating cover plate. The front side of the insulating cover plate is mounted on a collar of the end plate. The insulating cover plate, in the area of the pocket-type hollow spaces, has a radial recess with an interior edge which is disposed outside the hollow spaces. The connectors extend axially out of the pocket-type hollow spaces and are caused to be deflected approximately at a right angle radially with respect to the connecting points for the connectors in the axially aligned hollow spaces, through the recess by the collar means. The recess on its radial exterior side, is closed off by a ring wall section through which the strand connectors are caused to bend, in a second deflection and then are again led in an approximately axial direction. The strand connectors subsequently are again deflected in a radial direction.
Thus three approximately rectangular, deflections exist between the free strand ends and the connecting points of the strand connectors fitted into the pocket-type hollow spaces, thus ensuring a sufficient strain relief mounting for the connecting points. Compared to the initially mentioned known arrangement (DE-PS No. 21 36 170), there are essentially three advantages: (a) the strands do not have to be guided through an axial groove of the stator; (b) the strand connectors, in the area of the stator, are not subjected to the high operating temperature existing in the coils in the vicinity of the stator; and (c) the strand connectors may have an insulation covering of less high quality and resistance to heat.
As can now be appreciated, it is possible to insert the strand connectors, with their reinforced connecting points into the pocket-type hollow spaces, radially from the outside and prior to attaching the insulating cover. Because of the space provided near the end of an edge of the support plate, the cover can be first fitted on, causing the connector to bend because of a rib on an edge of the cover, as the insulating cover plate is axially attached and locked on the collar of the end plate. This eliminates the axial threading of the individual strand connectors into the recess of the insulating cover plate before it is placed onto the end plate. This results in considerable saving of work effort during assembly and also minimizes the number of work steps during manufacturing.
An additional advantage is obtained by the arrangement of a partition, extending axially as well as radially to the outside, to provide physical separation of the strand connector ends and thus phase insulation by the insulating cover plate. The winding of the coils on the stator, that is already equipped with the two side end plates, does not obstruct the way the stator plate bundle is covered by a ring disk of the external rotor on the front side. At this front side of the insulating cover plate, there is a cooperating locking mechanism between internal hubs similar to that utilized at the cover to anchor same in a form-locking way. The end plate and the insulating cover plate are thus used for the insulation, the stabilization and the front-side covering of the stator coils.
An additional benefit is obtained by providing a rib on a radial extending portion on the cover means to not only reinforce the insulating cover plate in the edge area of its recess, but to also provide an improved support for the rectangularly deflected strand connectors in the area of the pocket-shaped hollow spaces. Also, the placement of a rib on the cover plate radially outside of and spaced from the hollow axially extending pocket, to provide for bending of the connectors, has proved beneficial.
By providing the ring wall with an edge rib that projects radially inward, a reinforcement of the ring wall section and a better support of the strand connectors after the second deflection is also achieved.